The present invention relates to a new and improved position regulation system.
Generally speaking, the position regulation system of the present invention is of the type comprising a digital incremental measuring apparatus with a direction discriminator for the evaluation of measuring signals having 90.degree. phase shift. Such system contains two relatively movable objects, one of which is provided with a drive.
From German Pat. No. 2,758,525, published June 28, 1979, there is known to the art a digital incremental measuring apparatus with a direction discriminator, which serves to determine the relative position of two objects displaceable relative to one another. Since the resolution capacity of such measuring apparatuses is limited by the grid constant of the employed precision scale and by the counting frequency of the counters, the speed of advance of the relatively movable objects is increased so as to avoid a high resolution scale graduation. In order to achieve this, an up-down or forwards-backwards counter with a direction discriminator is used, which counts the signals which have a 90.degree. phase shift and are supplied by a scanning head sensing the scale graduation. Such signals are counted according to the principle of single evaluation, i.e. only the edge of the pulse corresponding to a change of the 90.degree.-signal is counted, whereas the 0.degree.-signal has the value 1. Then a division into any number of coded intermediate values is carried out by means of a circuit whose internal structure is not disclosed in the aforementioned patent. Thus, the graduation scale can be coarser in production to the factor by which the number of intermediate values is larger than the number of the measuring signals.
Such measuring apparatus is not suitable for a position regulation system containing two objects which are displaceable relative to one another and one of which objects has an incremental scale with a very fine graduation, such as 10 .mu.m, since the required high resolution of the measuring apparatus and the great length of the incremental scale would require counters with high capacity and a great circuit complexity.